Digital data encoding apparatus and method thereof
Digital data divided into blocks each having a predetermined number of samples is transformed into data on a frequency axis for each block to generate coefficient data for each frequency. Coefficient data of a predetermined number of blocks are stored in a buffer. From the buffer, coefficient data are inputted to a floating-point transforming circuit for each one block. The coefficient data are divided into a plurality of sub-bands, each sub-band including one or a plurality of coefficient data. The coefficient data are floating-point transformed for each sub-band and transformed into one sub-band common characteristic data which is common to the coefficient data included in each sub-band and mantissa data of the number equal to the number of coefficient data included in each sub-band. The sub-band common characteristic data and the mantissa data are stored in a memory. Sub-band common characteristic data of a predetermined number of blocks are read from the memory for each sub-band. One block-common characteristic data which is common to the read sub-band common characteristic data is generated. Coefficient data of a predetermined number of blocks are read from the memory for each sub-band. The read coefficient data is divided by an exponent expressed by the block-common characteristic data to generate new mantissa data.
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Claims
1. A digital data encoding apparatus for encoding digital data that is divided into blocks each having a predetermined number of samples, including:
- coefficient data generating means for generating coefficient data for each frequency by transforming said digital data into data on a frequency axis for each block;
- a buffer for storing said coefficient data of a predetermined number of blocks;
- floating-point transforming means for inputting said coefficient data for each one block from said buffer, dividing said inputted coefficient data into a plurality of sub-bands, each sub-band including one or a plurality of said inputted coefficient data, and floating-point transforming said divided coefficient data for each of said sub-bands to transform said divided coefficient data into one sub-band common characteristic data which is common to said divided coefficient data included in each of said sub-bands and mantissa data of which number is equal to the number of said divided coefficient data included in each of said sub-bands; and
- a memory for storing said sub-band common characteristic data and said mantissa data, wherein
- said floating-point transforming means
- reads said sub-band common characteristic data of said predetermined number of blocks from said memory for each of said sub-bands to generate one block-common characteristic data which is common to said read sub-band common characteristic data, and
- reads said coefficient data of said predetermined number of blocks from said memory for each of said sub-bands to generate new mantissa data by dividing said read coefficient data by an exponent expressed by said block-common characteristic data.
2. A digital data encoding apparatus according to claim 1, wherein
- said digital data is digital audio data, and
- said coefficient data generating means generates said coefficient data for each frequency by modified discrete cosine transforming said digital data for each block.
3. A digital data encoding apparatus according to claim 1, wherein
- said floating-point transforming means divides said inputted coefficient data so that a sub-band of a larger frequency includes more coefficient data.
4. A digital data encoding apparatus for encoding digital data that is divided into blocks each having a predetermined number of samples, including:
- coefficient data generating means for generating coefficient data for each frequency by transforming said digital data into data on a frequency axis for each block;
- a buffer for storing said coefficient data of a predetermined number of blocks;
- floating-point transforming means for inputting said coefficient data for each one block from said buffer, dividing said inputted coefficient data into a plurality of sub-bands, each sub-band including one or a plurality of said inputted coefficient data, and floating-point transforming said divided coefficient data for each of said sub-bands to transform said divided coefficient data into one sub-band common characteristic data which is common to said divided coefficient data included in each of said sub-bands and mantissa data of which number is equal to the number of said divided coefficient data included in each of said sub-bands; and
- a memory for storing said sub-band common characteristic data and said mantissa data, wherein
- said floating-point transforming means
- reads said sub-band common characteristic data of said predetermined number of blocks from said memory for each of said sub-bands to generate one block-common characteristic data which is common to said read sub-band common characteristic data, and
- reads said coefficient data of said predetermined number of blocks from said memory for each of said sub-bands only when at least one of differences between said generated block-common characteristic data and said read sub-band common characteristic data for said predetermined number of blocks is smaller than a predetermined value, to generate new mantissa data by dividing said read coefficient data by an exponent expressed by said block-common characteristic data.
5. A digital data encoding apparatus according to claim 4, wherein
- said digital data is digital audio data, and
- said coefficient data generating means generates said coefficient data for each frequency by modified discrete cosine transforming said digital data for each block.
6. A digital data encoding apparatus according to claim 4, wherein
- said floating-point transforming means divides said inputted coefficient data so that a sub-band of a larger frequency includes more coefficient data.
7. A digital data encoding method for encoding digital data that is divided into blocks each having a predetermined number of samples, including:
- a step for generating coefficient data for each frequency by transforming said digital data into data on a frequency axis for each block;
- a step for storing said coefficient data of a predetermined number of blocks into a buffer;
- a step for inputting said coefficient data for each one block from said buffer, dividing said inputted coefficient data into a plurality of sub-bands, each sub-band including one or a plurality of said inputted coefficient data, and floating-point transforming said divided coefficient data for each of said sub-bands to transform said divided coefficient data into one sub-band common characteristic data which is common to said divided coefficient data included in each of said sub-bands and mantissa data of which number is equal to the number of said divided coefficient data included in each of said sub-bands;
- a step for storing said sub-band common characteristic data and said mantissa data into a memory;
- a step for reading said sub-band common characteristic data of said predetermined number of blocks from said memory for each of said sub-bands to generate one block-common characteristic data which is common to said read sub-band common characteristic data; and
- a step for reading said coefficient data of said predetermined number of blocks from said memory for each of said sub-bands to generate new mantissa data by dividing said read coefficient data by an exponent expressed by said block-common characteristic data.
8. A digital data encoding method according to claim 7, wherein
- said digital data is digital audio data, and
- said coefficient data generating step generates said coefficient data for each frequency by modified discrete cosine transforming said digital data for each block.
9. A digital data encoding method according to claim 7, wherein
- said transforming step divides said inputted coefficient data so that a sub-band of a larger frequency includes more coefficient data.
10. A digital data encoding method for encoding digital data that is divided into blocks each having a predetermined number of samples, including:
- a step for generating coefficient data for each frequency by transforming said digital data into data on a frequency axis for each block;
- a step for storing said coefficient data of a predetermined number of blocks into a buffer;
- a step for inputting said coefficient data for each one block from said buffer, dividing said inputted coefficient data into a plurality of sub-bands, each sub-band including one or a plurality of said inputted coefficient data, and floating-point transforming said divided coefficient data for each of said sub-bands to transform said divided coefficient data into one sub-band common characteristic data which is common to said divided coefficient data included in each of said sub-bands and mantissa data of which number is equal to the number of said divided coefficient data included in each of said sub-bands;
- a step for storing said sub-band common characteristic data and said mantissa data into a memory;
- a step for reading said sub-band common characteristic data of said predetermined number of blocks from said memory for each of said sub-bands to generate one block-common characteristic data which is common to said read sub-band common characteristic data; and
- a step for reading said coefficient data of said predetermined number of blocks from said memory for each of said sub-bands only when at least one of differences between said generated block-common characteristic data and said read sub-band common characteristic data for said predetermined number of blocks is smaller than a predetermined value, to generate new mantissa data by dividing said read coefficient data by an exponent expressed by said block-common characteristic data.
11. A digital data encoding method according to claim 10, wherein
- said digital data is digital audio data, and
- said coefficient data generating step generates said coefficient data for each frequency by modified discrete cosine transforming said digital data for each block.
12. A digital data encoding method according to claim 10, wherein
- said transforming step divides said inputted coefficient data so that a sub-band of a larger frequency includes more coefficient data.
| 5294925 | March 15, 1994 | Akagiri |
| 5369724 | November 29, 1994 | Lim |
| 5394508 | February 28, 1995 | Lim |
| 5625746 | April 29, 1997 | Lim |
| 5642111 | June 24, 1997 | Akagiri |
- Chen et al. "Sub-Band Coding of Audio Using Recursively Indexed Quantization." Applications of Signal Processing to Audio and Acoustics, 00, 1995. Furui et al., Advances in Speech Signal Processing, Marcel Dekker, Inc., pp. 109-141, 1991. Princen et al., Analysis/Synthesis Filter Bank Design Based On Time Domain Aliasing Cancellation, IEEE Transaction on Acoustic, Speech, and Signal Processing, ASSP-34, No. 5, pp. 1153-1161, Oct.1986.
Type: Grant
Filed: Aug 29, 1996
Date of Patent: Sep 22, 1998
Assignee: Nippon Steel Corporation (Tokyo)
Inventor: Toru Chinen (Tokyo)
Primary Examiner: Allen R. MacDonald
Assistant Examiner: Alphonso A. Collins
Law Firm: Pollock, Vande Sande & Priddy
Application Number: 8/697,728
International Classification: G10L 914; G10L 916;
